An automatic testing machine (ATM) operates in a production environment to rapidly and accurately test the operation and performance of various types of devices under test (DUT), including computer devices and communication devices. The DUTs could be a finished product or a component of a larger system.
The ATM is programmed to perform various tests on the DUT automatically. For example, a microcomputer chip DUT may be fed power and known input signals, and the output signal of the DUT compared with expected results. Another example is where RF signals are transmitted to a finished cellular telephone DUT to determine if the telephone properly operates. Other tests could include environmental tests, such as temperature or vibration tests.
Depending upon the nature and number of the tests being performed, the testing may last from a couple of milliseconds to several minutes. The information from the testing is compared with expected test results. If there is some defect such that the DUT falls below specifications, the ATM will designate the DUT as failed, either by marking the DUT, placing the DUT in a failure area, or indicating the failure to an operator.
The ATM is then loaded with the next DUT, either manually or automatically, and the testing procedure is repeated for this next DUT. This testing information from the testing can be used to evaluate the fabrication process for possible changes, as well as to perform failure analysis on individual failed devices.
Typically, each ATM is designed to perform a specific class of tests on the DUT, and are not able to perform other classes of tests. For example, a vibration ATM may not be able to perform electrical signal tests. However, different types of DUTs may require the same tests to be performed. For example, all types of microcomputer chips are tested for electronic performance characteristics, but different chips will have different locations for power, inputs and outputs. ATMs are made flexible by the use of test fixtures. The test fixture provides an interface between the device under test DUT and the ATM. Thus, a single ATM can perform tests on different types of devices when connected via different fixtures.
As shown in FIG. 3, ATM 31 is connected to DUT 32 via fixture 33. Fixture 33 is connected to ATM 31 via connections 34. For the sake of simplicity, only five connections 34 are depicted, however, depending on the nature of the DUT and the tests being performed, more or less connections 34 may be required. For example, typical connections to perform an operational test on a cellular telephone may require one high voltage connection, 8 ganged electrical connections comprising 90 electrical connections, 6 RF connections, and 36 or more pneumatic connections.
The number of connections 34 between fixture 33 and ATM 31 causes problems when fixture 33 needs to be changed. For example, fixture 33 would need to be changed when a different type of DUT 32 is going to be tested or if fixture 33 malfunctions in some manner and requires either repair or replacement. While fixture 33 is being replaced, the production line is necessarily halted. The large number of connections which first have to be removed, and then properly replaced is extremely time consuming, often requiring 10 or more minutes of production line downtime.
Moreover, if the connections are improperly made, then incorrect information about DUT 32 may be collected. The incorrect information could lead to improperly passing a defective DUT or failing a passing DUT. The incorrect information may also result in incorrect or unnecessary changes being made to the production process. Also if the connections are improperly made, then damage may occur to the DUT. For example, incorrectly connecting a power supply to a data input may destroy the computer microchip of the DUT. Furthermore, the connectors on the ends of connections 34 are typical fragile, and thus can easily be damaged during fixture 33 replacement, particularly if the connector is incorrectly oriented during insertion. However, the connectors are also susceptible to damage from normal wear and tear incurred during fixture replacement. This is due to the slight misalignment that occurs when operators manually plug and unplug connectors from fixture 33.
Other problems that could arise because of connections 34 include cross-talk, cross-coupling, or other forms of mutual interference. This would occur when critical lines of connections 34 are positioned too close to each other. This could cause the collection of incorrect information about DUT 32. The incorrect information could lead to improperly passing a defective DUT or failing a passing DUT. The incorrect information may also result in incorrect or unnecessary changes being made to the production process. For example, an input signal is crossed onto a second input line, which causes a different output than is expected, and thus the passing DUT is failed.
Therefore, there is a need in the art for an apparatus and method that allows for the rapid and reliable replacement of ATM fixtures in a production environment with a low potential for connector damage.